1. Technical Field
The present invention relates to a vertical cavity surface emitting laser and an atomic oscillator.
2. Related Art
The vertical cavity surface emitting laser (VCSEL) is, for example, used as a light source of the atomic oscillator using coherent population trapping (CPT) which is one of the quantum interference effects.
In the vertical cavity surface emitting laser, a resonator generally has an isotropic structure, and accordingly it is difficult to control a polarization direction of laser light emitted from the resonator. JP-A-2001-189525, for example, discloses a vertical cavity surface emitting laser which applies an anisotropic stress to a resonator (active layer) by an insulation layer which is formed to come in contact with an outer surface of a columnar semiconductor deposition body including a part of the resonator, and controls a polarization direction of laser light to a specific direction.
In the vertical cavity surface emitting laser disclosed in JP-A-2001-189525, an upper electrode is formed so as to cover most of the upper surface of the insulation layer.
Therefore, in the vertical cavity surface emitting laser, it is important to decrease parasitic capacitance, in order to improve high frequency characteristics.
However, in the vertical cavity surface emitting laser disclosed in JP-A-2001-189525, since the upper electrode is formed so as to cover most of the upper surface of the insulation layer, it is difficult to sufficiently decrease the parasitic capacitance.